- VPA has been associated with neural tube defects in the developing human fetus, for this reason and because FEC100 used in this trial are also known to be teratogenic, women of child-bearing potential and men must agree to use adequate contraception (hormonal or barrier method of birth control; abstinence) prior to study entry and for the duration of study participation. Participating men must use condoms while on study and for at least 3 months after the trial has ended. Should a woman become pregnant or suspect she is pregnant while participating in this study, she should inform her treating physician immediately.